1. Technical Field
The present invention relates to a method for adjusting certain performance characteristics of head suspensions used in rigid disk drives. In particular, the present invention includes a method for adjusting the static attitude of head sliders used on rigid disk drive type head suspensions.
2. Background of the Invention
Head suspensions are well known and commonly used within dynamic magnetic or optical information storage devices or drives with rigid disks. The head suspension is a component within the disk drive which positions a magnetic or optical read/write head over a desired position on the storage media where information is to be retrieved (read) or transferred (written). Head suspensions for use in rigid disk drives typically include a load beam that generates a spring force and supports a flexure. The flexure has a slider bond pad to which a head slider supporting a read/write head is to be mounted. The load beam typically includes a base at a proximal end, a rigid region at a distal end, and a spring region between the rigid region and the base for providing the spring force. Head suspensions are normally combined with an actuator arm or E-block to which the base of the load beam is mounted so as to position (by linear or rotary movement) the head suspension, and thus the head slider and read/write head, with respect to data tracks of the rigid disk.
The head slider is aerodynamically designed so as to allow the head slider to "fly" on an air bearing generated by the spinning rigid storage disk. The spring force urges the head slider in a direction opposing the force generated by the air bearing. The point at which these two forces are balanced during operation is the "fly height" of the head slider. The flexure permits pitch and roll motion of the head slider and read/write head as hey move over the data tracks of the disk. The flexure does this by providing a gimbal connection between the head slider and load beam. Such a gimbal connection can be provided in numerous ways, including via a flexure which is formed separately from the load beam and then attached thereto and a flexure which is formed integrally with the load beam. One method, which utilizes a separately formed flexure, involves supporting the head slider on a resilient tongue which is in turn supported between resilient lateral arms connected to a flexure mounting region, which is where the flexure connects to the load beam. The slider bond pad is located on the tongue and supports the head slider. The spring force provided by the spring region of the load beam is transferred to the flexure via a load point dimple, which can be a rounded protrusion provided between the load beam and the flexure. The resilient lateral arms allow the gimbal connection of the tongue to move in pitch and roll directions to accommodate surface variations in the spinning magnetic disk over which the slider is flying. The roll axis is a longitudinal axis of the head suspension (typically at its longitudinal center line). The pitch axis is perpendicular to the roll axis, that is, is transverse to the load beam, and crosses the roll axis at or near the head slider.
In order to store and retrieve data from magnetic or optical disks on which data is densely packed, it is necessary for the head slider to fly closely above the surface of the spinning data disk (on the order of 0.1 .mu.m) without colliding with the disk. Further, because of the dense packing of data on magnetic or optical disks, it is important for the read/write head attached to the head slider to be able to read from or write to a relatively small area or spot on the disk.
In relation to this, an important performance criteria of a head suspension is the orientation or attitude of the head slider as it flies over a disk surface. This orientation or attitude can be termed "slider flying attitude" and refers to the positional orientation of the head slider with respect to the surface of the disk when the head suspension is "loaded," that is, under the influence of the balanced forces created by the spring force and the air bearing. When the head suspension is not actually flying over a spinning disk, this loaded state can be simulated. This can be done by applying a force in the same direction as the air bearing force at a point on the head suspension other than the head slider or, if the slider is not attached, a head slider bond pad where the head would be attached. This force is applied to lift the head slider to its loaded position or loaded state at fly height. The orientation or attitude of the head slider or slider bond pad under this simulated loaded state is referred to as "static attitude." The difference or bias between the slider flying attitude and static attitude can be measured for a given head suspension so that a measurement of the static attitude, which can be an easier measurement to make than slider flying attitude, can be used to determine slider flying attitude.
Static attitude of a head slider can be measured with reference to pitch and roll axis of the head suspension. Roll is measured as the amount of rotation of the head slider about the roll axis and pitch is measured as the amount of rotation of the head slider about the pitch axis. The head slider is typically designed to have a predetermined or desired static attitude. Deviations from a desired static attitude can be quantified as pitch and/or roll errors. For pitch or roll errors to exist, there must be a torque or moment of force exerted on the head slider in the direction of rotation of the head slider from its desired static attitude. Such torque can have either or both a pitch component and/or a roll component.
Pitch and roll errors can be caused by manufacturing variations of the head suspension, handling of the head suspension and related components after and during manufacturing, or contamination of the head suspension by airborne foreign matter. If pitch and/or roll errors exist in the static attitude of a head slider, there is a greater possibility that the head slider might impact the disk surface. Further, errors in static attitude of the head slider cause the read/write head to be out of proper orientation to the surface of the disk or closer or further from the disk surface than it is designed to be. As such, the read/write head may not be able to "focus" on as small an area or spot on the disk as necessary to efficiently transfer data to or from the disk. Also, the head can be improperly positioned with respect to a specific track. This can degrade disk drive performance.
Because of the importance of correct head slider static attitude, various methods exist for correcting pitch and roll errors to obtain appropriate static attitude. Such methods are disclosed in, for example, U.S. Pat. No. 5,682,780, issued Nov. 4, 1997 to Girard for "Gram Load, Static Attitude And Radius Geometry Adjusting System For Magnetic Head Suspensions"; U.S. patent application Ser. No. 08/657,778, filed May 31, 1996 for "Gram Load, Static Attitude And Radius Geometry Establishing System For Flat Magnetic Head Suspensions"; U.S. patent application Ser. No. 08/706,792, filed Sep. 3, 1996 for "Gimballing Flexure With Static Compensation And Load Point Integral Etched Features", and U.S. patent application Ser. No. 08/697,923, filed Sep. 3, 1996 for "Method Of Mounting a Head Slider To a Head Suspension With Static Offset Compensation" each of the above are commonly owned by the assignee of the present application, and are fully incorporated herein by reference.
One method of correcting erroneous static attitude of the head slider involves altering the profile of the load beam. In this method, the profile of the load beam can be altered to support the flexure at an attitude to the disk surface which compensates for any erroneous attitude of the head slider. That is, through altering the load beam, the flexure position can be altered to compensate for pitch and/or roll error of the head slider. By adjusting the load beam in this way, however, other head suspension parameters, such as fly height, gram load and resonance profile can be unnecessarily affected. Further, it is known to form electrical leads on the load beam for carrying electronic read/write signals from the read/write head to data electronics. These electrical leads can be relatively delicate, and it can be difficult to alter the profile of the load beam without adversely affecting the delicate electrical leads.
Another method of correcting erroneous static attitude of the head slider involves directly adjusting a gimbal region of the flexure. For example, with regard to the gimbal region described above, the attitude of the resilient lateral arms supporting the tongue or the tongue itself could be adjusted to correct the static attitude of the head slider mounted to the tongue.
Additionally, some methods of adjusting static attitude require the adjustment to take place prior to mounting the head suspension to an actuator arm or E-block. Variations in head slider static attitude, however, could occur during such mounting procedures, either through handling or affects of actuator arm attitude on head slider attitude. These variations could not be corrected using such methods.